ABSTRACT: Fundamental organizational and financial changes in substance abuse treatment services are taking place as both public and private sectors attempt to manage the care of clients in order to achieve cost containment. Managed care system can, in addition to containing costs, increase the availability and quality of treatment to those who need the care. On the other hand, cost containment can lead to denial of needed treatment and reduced quality of care (Mechanic, et al. 1995). This depends, at least in part, on the use of procedures that address equitable access and quality, as well as costs. the Santa Clara County (California) Department of Alcohol and Drug Services is creating an outcomes- and quality-oriented system to manage care. We propose a natural experiment that compares access, costs, outcomes, and cost effectiveness in this county's managed care system to two counties without substantial managed care characteristics. Baseline and outcome data will be collected for randomly selected clients from each county during calendar year 2000. Clients will be followed for 12 months after admission. Major project goals are to investigate: 1) the relative equity of access to services for special (women and ethnic minority) populations; 2) the relative severity of substance abuse clients upon entry to treatment; 3) the relative costs of treatment per client; 4) relative client satisfaction and outcomes (substance abuse, medical, legal, family/social, employment, and psychiatric); and 5) cost effectiveness of care along the same dimensions. Important subgroups of clients will also be analyzed; a) substance abusers with and without psychiatric co- morbidity; b) male and female clients; c) Caucasian and Latino/Hispanic clients; and d) Caucasian and all ethnic minority clients.